Abstract: Disclosed is a one-component type magnetic developer consisting essentially of a particulate shaped article of a composition comprising a binder resin medium and a powdery magnetic material dispersed in the binder resin medium, wherein said magnetic material comprising (A) a non-pulverizing agglomerate of cubic particles of magnetite having a particle size of 1 to 10 .mu.m as measured by an electron microscope and (B) magnetite particles having a particle size of 0.2 to 1 .mu.m at an (A)/(B) weight ratio of from 95/5 to 10/90, especially from 95/5 to 30/70.

Abstract: Disclosed is a two-component type magnetic developer comprising a magnetic carrier consisting of a non-pulverizing agglomerate of cubic particles of magnetite having a particle size of 1 to 14 microns as measured by an electron microscope and a magnetic toner having a high electric resistance and consisting of particles having a particle size of 3 to 30 microns and comprising a binder resin medium and magnetite having a particle size smaller than 1 micron, which is dispersed in the binder resin medium, the magnetic carrier/magnetic toner mixing weight ratio being in the range of from 5/100 to 40/100.

Abstract: Disclosed is a dry composite magnetic developer consisting essentially of a particulate shaped article of a composition comprising a binder resin medium and a powdery magnetic material dispersed in the binder resin medium, wherein said developer is formed by dry blending (A) a first particulate shaped article comprising a non-pulverizing agglomerate of cubic particles of magnetite having a number average particle size of 1 to 10 .mu.m as measured by an electron microscope with (B) a second particulate shaped article comprising magnetite particles having a particle size of 0.2 to 1 .mu.m at an (A)/(B) weight ratio of from 95/5 to 10/90, especially from 95/5 to 30/70.

Abstract: Disclosed is a dry magnetic developer consisting essentially of a particulate shaped article of a composition comprising a binder resin medium and a powdery magnetic material dispersed in the binder resin medium, wherein said composition comprises as the powdery magnetic material a non-pulverizing agglomerate having a secondary particle size of 1 to 10 microns, which is formed by granulating and sintering fine cubic particles of magnetite or other ferrite having a primary particle size of 0.1 to 1 micron.

Abstract: A two-component dry-type composite developer which is a mixture of 100 parts of (A) magnetic toner particles of a binder resin and 40 to 70% by weight of magnetite having a bulk density of at least 0.45 g/ml, a number average maximum size of at least 0.5 .mu.m and a maximum size/minimum size ratio of from 1.0 to 5.5 and 1 to 30 parts of (B) non-magnetic toner particles of binder resin, pigment and negative charge controlling agent. The magnetic toner particles have an electrostatic capacitance of 7 to 8.5 picofarad, a dielectric constant of 3.59 to 4.36, and a volume resistivity of 1.2 to 8.6.times.10.sup.14 .OMEGA.-cm, and the nonmagnetic toner particles have an electrostatic capacitance of 6.0 to 8.0 picofarad and a dielectric constant of 3.08 to 4.10. The toner particles (A) and (B) have friction chargeability characteristics of the same polarity and are consumed at the same rate during development such that the mixing ratio remains constant and the development characteristics are not changed during use.

Abstract: Disclosed is an electrically insulating, magnetic one-component type developer comprising an electrically insulating binder medium, and a magnetic material powder and a charge control agent dispersed in the binder medium, wherein the charge control agent comprises a negative or positive charge control agent and a charge control agent having a polarity opposite to that of said charge control agent at a weight ratio of from 1/0.05 to 1/1.5.